2KXG:
reference: Solution structure of the squash aspartic acid proteinase inhibitor (SQAPI) and mutational analysis of pepsin inhibition., Headey SJ, Macaskill UK, Wright MA, Claridge JK, Edwards PJ, Farley PC, Christeller JT, Laing WA, Pascal SM, J Biol Chem. 2010 Aug 27;285(35):27019-25. Epub 2010 Jun 9. PMID: 20538608

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).